1. Field of the Invention
The present invention is related to a luminescence device and more particularly to an organic electro-luminescence device.
2. Description of Related Art
Displays having the features of light weight and high efficiency, such as liquid crystal displays (LCDs), have now been extensively developed. However, LCDs still have many problems that are yet to be overcome, such as limited viewing angle and unsatisfactory response time. Due to these problems, LCDs are not suitable for displaying high-speed motion pictures, and LCDs require backlight plates which increases power consumption.
In recent years, the technology of flat-panel display, i.e. organic electro-luminescence display, has been developed to solve the foregoing problems. Compared with other types of flat-panel display technology, an organic electro-luminescence display has potential to become the mainstream in the next generation, for it has the advantages of self-luminescence, no viewing angle dependence, power saving, simple manufacturing process, low costs, low working temperature, quick response speed, and full color.
The organic electro-luminescence display is a device which utilizes the luminescence properties of organic luminescence materials to achieve display effects, and is mainly constituted by a pair of electrodes and an organic light emitting layer, wherein the organic light emitting layer includes organic light emitting materials. When current passes through an anode and a metallic cathode, electrons and holes are combined in the light emitting materials to generate excitons, which transform the energy therein into light for display effects.
In an organic polymer luminescence device, the organic light emitting layer is usually formed by mixing more than two types of materials, such as polymer and small molecule, so as to obtain favorable light emission efficiency. However, when a separation phenomenon occurs between the materials of the organic light emitting layer, the light emission efficiency of the polymer device would be greatly reduced. More specifically, if the mixture of the polymer and small molecule is not proper, energy cannot be effectively transferred between the polymer and the small molecule. In addition, if the materials forming the organic light emitting layer occur phase separation phenomenon, the surface of the whole organic light emitting layer becomes uneven, which causes electric leakage and decreases the light emission efficiency.
Conventionally, CsF/Al is adopted to form a stacked electrode which serves as the cathode. The light emission efficiency of the organic electro-luminescence device is very sensitive to the thickness of the CsF layer in the cathode. For instance, the performance of the whole device may be greatly impaired if the CsF layer is too thin or too thick. For this reason, the control of the fabricating process of the organic electro-luminescence device is crucial. Any variations to the thickness of the CsF layer may impair the yield and reproducibility.
Therefore, in addition to brightness and light emission efficiency, the difficulty in process control and production costs should also be taken into consideration when fabricating the organic electro-luminescence device. How to enhance the brightness and light emission efficiency and meanwhile increase production quantity to maintain the yield and reproducibility has become an important issue.